The present invention relates to an electrographic copying apparatus, and more particularly, it relates to a wet type electrographic copying apparatus which uses liquid developer.
A wet type electrographic copying apparatus comprises: a paper feeding device which inserts a photosensitive paper into the apparatus; a charging device which charges the paper surface; an exposure device which exposes the paper corresponding to an original; a developing device which comprises a developer vessel, a developer feed pump and pressing rollers for removing excessive developer from the paper; and a paper conveyer device. In the conventional wet type electrographic copying apparatus, each device is caused to start to operate simultaneously with the other devices by a start signal, and is controlled individually regardless of the condition of the other devices. For example, the photosensitive paper is exposed immediately after it is transferred to the exposure position without a delay, thereby causing a blur of the image caused by the vibration of the conveyor belt due to its elasticity. During operation, the liquid developer is always circulated by the feed pump, causing a large evaporation loss. In addition, it is not easy to replenish or exchange the developer, because the feed pump is fixed within the developer vessel.
A prior art mechanism of the pressing rollers of the developing device is illustrated in FIG. 8. In FIG. 8, a lever 31 is pivotablly mounted on each side wall 30. The lever 31 has two arms 31a, 31b. The arm 31a engages with one of roller shafts 32. The other arm 31b is connected to a spring 33. In this arrangement, a pair of rollers 34, 34' are pressed against each other by the pulling force of the spring 33. An eccentric roller 35, which engages with the lever 31, is arranged on each side wall 30. The rollers 34, 34' are released from the spring force by rotating the eccentric roller 35 so as to rotate the lever 31 in the direction P when the paper is jammed between the rollers 34, 34' or the rollers are taken out of the apparatus for repair or cleaning. However, the lever 31 must be shifted against the spring force over a relatively large range in order to take out the rollers 34, 34'. Accordingly, the dimensions of the eccentric roller 35 must be large and it is not easy to rotate such a large eccentric roller against the force of the spring 33.